Professor Herman Bondi, one of the proponents of the Steady State Theory, presented this volume as an account that would establish cosmology as a distinct branch of physics. First published in 1952, just a few years after the term 'the Big Bang' was coined, it represents an important stage in the development of cosmology. With detailed discussions of different theories including Newtonian cosmology, relativistic cosmology and kinematic relativity, it gives a remarkable insight into scientific thought at this crucial time. It will be most useful to anyone with an interest in the history of science or the progression of scientific ideas.